Codes came up reading PO170(bank1)and PO173(bank2). Need some help. on 1997 Mitsubishi 3000GT SL

These codes came up and my car is running really rich. The person that I bought it from said he replaced part of the exhaust because of a leak. I just cleared the codes and my car started stalling after that all the way home. It was idling way to low. It finally stopped stalling and is idling just fine. It usually runs fine with no problems but I wanna fix it. Any suggestions?

Asked by for the 1997 Mitsubishi 3000GT SL
U gotta see what those codes r ,I believe there o2 sensor codes, u gotta check o2 sensor or bad cats..